1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus, particularly to a sheet feeding apparatus in which a second sheet stacking portion is detachably attached to a first sheet stacking portion and an image forming apparatus containing such a sheet feeding apparatus.
2. Description of the Related Art
Recently, an image forming apparatus such as a copying machine, a printer, and a facsimile, in which the sheet is fed from the sheet feeding apparatus to the image forming portion to form an image is widely spread. Usually, in the sheet feeding apparatus, a sheet cassette that is of a sheet storage portion is detachably attached to an apparatus main body, and the sheet stored in the sheet cassette is automatically fed to the image forming portion.
In some of the sheet cassettes used in sheet feeding apparatus, an intermediate plate on which the sheets are stacked to press the sheet against a sheet feeding roller is provided while being able to be lifted and lowered. In the sheet cassette in which the intermediate plate is provided, a trailing end regulating member that regulates a position of a trailing end in a feeding direction of the sheet stacked and stored on the intermediate plate (hereinafter referred to as trailing end) is provided so as to enable storage of sheets having different sizes. A side end regulating member is also provided to regulate a side end position in a direction (hereinafter referred to as width direction) orthogonal to the sheet feeding direction.
In the sheet cassette, the sheet trailing end is regulated by the trailing end regulating member while the sheet side end is regulated by the side end regulating member, whereby the sheet leading end is always regulated at a predetermined position. Therefore, the sheet can stably be fed irrespective of the sheet size when the sheet cassette is stored in the apparatus main body.
Recently, the demand to form an image in a small-size sheet that is of an irregular size sheet such as a 4-by-6-inch-size sheet and a postcard-size sheet in addition to a special sheet has increased for image forming apparatus such as the laser beam printer.
However, for example, when the small-size sheet is set in the sheet cassette, the small-size sheet is located outside a range where the side end regulating member and the trailing end regulating member are moved. Therefore, when the small-size sheet is set in the sheet cassette, the position of the sheet cannot be regulated by the side end regulating member and the trailing end regulating member.
In order to regulate the small-size sheet whose position cannot be regulated by the regulating member, for example, Japanese Patent Application Laid-Open No. 2005-263450 discloses a technique in which the side end regulating member can be moved to a position that regulates the small-size sheet. The intermediate plate is notched in the width direction in order to enable the side end regulating member to be moved in the width direction.
Japanese Patent Application Laid-Open No. 11-217123 discloses a technique in which an attachment is attached to the side end regulating member. Japanese Patent Application Laid-Open No. 11-059925 discloses a technique in which a dedicated cassette that is of a small-size-sheet regulating member is detachably attached to the sheet cassette.
However, in the conventional sheet feeding apparatus and image forming apparatus, when the intermediate plate is notched such that the side end regulating member can be moved in the width direction, it is necessary that the intermediate plate is largely notched in order to enable the side end regulating member to be moved to the position that regulates the small-size sheet. When the attachment is attached to the side end regulating member, it is necessary that the attachment is moved to the side end position of the small-size sheet. Therefore, it is necessary to largely notch the intermediate plate. A strength of the intermediate plate is decreased when the intermediate plate is largely notched.
On the other hand, when the dedicated cassette is detachably attached to the sheet cassette, it is not necessary to largely notch the intermediate plate. However, the sheet cannot stably be fed because the side end regulating member that regulates the sheet position in the width direction is not provided in the dedicated cassette. Even if the side end regulating member is provided, a mechanism for fixing the side end regulating member moved to a side end regulating position is required to stably feed the sheet. When the mechanism is provided, a configuration of the dedicated cassette becomes complicated and cost is increased.
The present invention provides a sheet feeding apparatus and an image forming apparatus, in which a sheet can stably be fed with a simple configuration without decreasing strength of an intermediate plate.